UML diagrams - using case tools

Does anyone have an idea about UML diagrams using case tools?
Why we go for java coding o/p for UML diagrams...
Is it possible for any other languages like C,C++ etc?
What is the use of it?
How to build a UML diagrams?
I know few basics of it thought i feel difficult to draw it.
Thanks in advance.

There are other case tools for generating code in C,PHP, et al as well. Check out ArgoUML, its an collaboration effort for opensource case tools. Although it itself is java based, but it can generate PHP code as well.